ATMakers emailed and asked if we'd make a Trinkey (https://www.adafruit.com/search?q=trinkey) with a TRRS jack (https://www.adafruit.com/product/5764) on the end, for making customizable HID devices that use simple 3.5mm audio jack connectors. ideally something that will make AT - Accessibility Technology - projects EZ to build and maintain.
here's our take on it, what's interesting is each pin of the jack - including the two switches for tip and ring1 - connect to GPIO / analog inputs on the SAMD21. there's no pre-defined VCC or GND because different switch and joystick makers have different configurations and we might want to change around what pins are power, ground, pullups, etc!
this board will be great for use with CircuitPython to make any sort of AT switch or potentiometer interface super fast, to demo it we've written up a quick CPy sketch that will listen for two switches, and when they're pressed, blink the NeoPixel and emit keypresses as if its a keyboard.